I second seriously considering mediation. But you need to be clear on what mediation offers. A mediator does not offer their opinion on a possible solution rather their role is to assist both sides to look at everything and decide between the two the best possible outcome.
So if both parties can see the big picture and realise that it's not about "winning" but rather coming out with the least objectionable result for both then happy days. However if one person becomes bogged down in their own position and can't be swayed to compromise then its a different ball game.
From personal experience i would recommend you be honest with yourself about what your red line issues are and what areas you're happy to give leeway on. Bear in mind that a full blown court proceedings will quickly add 20k to your costs and maybe that will help focus your mind.
If there is alot of emotion still involved I would also recommend attending a counsellor. It's useful to vent in that space with an independent third party and then be focused and less emotional when trying to negotiate.
I've used both private mediation and the free service offered by the legal aid board. I found both excellent if ultimately ineffective through no fault of theirs.